The present invention relates to a folded type portable telephone set, and more particularly to a set for confirming the impossibility of communications because the portable telephone set is in "OUT OF BOUNDS" of a service area which enables communications and then automatically informing, if the portable telephone set moves from "OUT OF BOUNDS" to "WITHIN BOUNDS" of the service area which enables communications while a user moves carrying the portable telephone set in its folded state, the user of the entry to the area of "WITHIN BOUNDS" by an informing sound or vibration.
For example, as disclosed in JP-A-163638/1996, a conventional folded type portable telephone set is constructed in such a manner that even if the portable telephone set is carried in its folded state, by operating a button switch provided in the side face of a main body to actuate displaying means also provided in the side face and having WITHIN BOUNDS/OUT OF BOUNDS display functions, a user of the portable telephone set can be informed as to whether he is in WITHIN BOUNDS of a service area for communications or OUT OF BOUNDS for non-communications. Normally, if a radio wave from a base station cannot be received by an electric field strength of a fixed level or higher even if the user is in a service area, "OUT OF BOUNDS" is displayed. However, if "OUT OF BOUNDS" is displayed when the user of the folded type portable telephone set operates the button switch and actuates a display for displaying in order to make a call, then the user must move for a while and operate the button switch again to actuate the displaying means for displaying. Consequently, it was necessary for the user of such a folded type portable telephone set to repeat the foregoing operations until the display of "WITHIN BOUNDS" appeared. With the foregoing conventional folded type portable telephone set, when the user of the portable telephone set operates the button switch and actuates the displaying means to display "WITHIN BOUNDS" or "OUT OF BOUNDS" in order to make a call, If the display of "OUT OF BOUNDS" appears, the user must move for a while and operate the button switch again to instruct the displaying means to perform displaying. Thus, the conventional folded type portable telephone set is disadvantageous in that until the display of "WITHIN BOUNDS" appears, the user must move around and repeat the foregoing operations.